caltrop

noun

1. tropical annual procumbent poisonous subshrub having fruit that splits into five spiny nutlets; serious pasture weed

   noun.plant

   Source: WordNet 3.0

2. a plant of the genus Trapa bearing spiny four-pronged edible nutlike fruits

   noun.plant

   Synonyms water chestnut water chestnut plant

   Source: WordNet 3.0

3. Mediterranean annual or biennial herb having pinkish to purple flowers surrounded by spine-tipped scales; naturalized in America

   noun.plant

   Synonyms centauria calcitrapa star-thistle

   Source: WordNet 3.0

4. A genus of herbaceous plants (<i>Tribulus</i>) of the order <i>Zygophylle&aelig;</i>, having a hard several- celled fruit, armed with stout spines, and resembling the military instrument of the same name. The species grow in warm countries, and are often very annoying to cattle.

   noun

   Source: webster1913